Electrochemical performances of AB 5-type hydrogen storage alloy modified with Co 3O 4

Abstract

Anodic electrodes with the mixture of hydrogen storage alloys and different contents of Co 3O 4 (2%, 4%, 6% and 8%, mass fraction) powders were made. The effects of Co 3O 4 on the electrochemical performance of the alloy electrodes were studied. The constant charge-discharge tests show that the discharge capacity of alloy electrodes with Co 3O 4 significantly increases, and the maximum discharge capacities of electrodes with 2%, 4%, 6% and 8% Co 3O 4 are higher than the electrode with no Co 3O 4 by 0.83%, 4.86%, 7.18% and 9.21%, accordingly. Linear polarization (LP) and electrochemical impedance spectroscopy (EIS) tests suggest that charge-transfer resistance decreases by the addition of Co 3O 4. Cyclic voltammogram (CV), scanning electron microscopy (SEM) and energy dispersive spectrum (EDS) tests indicate that Co 3O 4 can partly dissolve and experience a reversible oxidation-reduction process of Co to Co (OH) 2, leading to the improvement in the electrochemical performance of hydrogen storage alloy.